Because respiratory disease frequently results in regional differences in lung expansion, a long term goal is to understand the physiological implications of nonuniform lung expansion on the distribution of ventilation and pulmonary perfusion. Maldistribution of ventilation or perfusion results in inefficient and potentially inadequate gas exchange. This proposal will utilize a fluid mechanical analysis to evaluate the pressure-airflow relationships in small airways in excised dog and pony lungs which have been treated to stimulate airway or parenchymal disorders. A radiographic technique will then be used in excised dog and pig lungs to confirm these effects by evaluating small airway pressure-diameter behavior during nonuniform lung expansion. A model which considers airways as compliant tubes embedded in an elastic continuum will be used in conjunction with the pressure-diameter data to quantify the mechanical interactions of pulmonary parenchyma and small airways. Several species with widely differing lungs, will be studied to determine the validity of the model. Finally, the effect of nonuniform lung expansion in regional blood flow in peripheral lung regions will be examined using radiolabeled microspheres. Anesthetized dogs and pigs will be studied. By quantifying the mechanical interactions of pulmonary parenchyma, small airways and blood vessels, it is hoped that pulmonary disease processes and therapeutic interventions such as high frequency oscillation which cause nonuniform lung expansion may be better understood.